12 October 2007. The question of whether antipsychotic drugs reduce cognitive impairment in schizophrenia has ramifications beyond patient care. Even modest cognitive benefits of these drugs would justify further efforts to maximize effects on the putative molecular mechanisms (see SRF Forum Discussion). Two recent, and prominent, studies, led by Richard Keefe of Duke University, suggest that second-generation antipsychotics, and even a first-generation one, enhance cognition in subjects with schizophrenia. However, in the October Archives of General Psychiatry, Terry E. Goldberg and colleagues at Zucker Hillside Hospital in Glen Oaks, New York, show that practice effects from repeated test taking can masquerade as drug benefits.

The cognitive deficits at issue in schizophrenia cross multiple domains, including attention, working memory, language skills, executive function, and social cognition (for a review, see Bowie and Harvey, 2005). Their importance for functional outcomes has led researchers to examine antipsychotic drugs as possible remedies. According to a 2005 meta-analysis, atypical, or second-generation, antipsychotics improve cognitive functioning more than older, typical antipsychotics (Woodward et al., 2007).

Equal “gains”
Yet the research may be biased by methodological shortcomings and industry sponsorship, Keefe and colleagues write in the June Archives of General Psychiatry. They sought to minimize such problems by comparing the cognitive effects of four atypical and one typical antipsychotic as part of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) study (see SRF related news story). Their study randomly assigned subjects with chronic schizophrenia to treatment with an atypical antipsychotic—namely, risperidone, ziprasidone, quetiapine, or olanzapine—or the typical antipsychotic pherphenazine. Analyses included 817 subjects who completed cognitive testing at baseline and after 2 months of treatment.

Over time, all groups in the double-blind study improved their cognitive test performance to a small but statistically significant extent. Unexpectedly, they all did so equally.

The researchers write, “This failure to document a neurocognitive advantage of second-generation antipsychotics suggests that the positive findings from prior reports may not generalize well to the type of everyday clinical practice examined in the CATIE trial.” They contrast their study with others that used “high dosages of first-generation antipsychotics, usually haloperidol, creating an unfair comparison because of the increased risk of extrapyramidal symptoms and anticholinergic treatment, which may impair cognition.”

The other randomized, double-blind study headed by Keefe appeared in the July American Journal of Psychiatry. It compared the cognitive effects of three second-generation antipsychotics in 224 subjects with early schizophrenia who completed cognitive testing after 12 weeks of treatment.

The risperidone, olanzapine, and quetiapine groups initially showed similar, modest gains in performance. However, by week 52, those gains no longer reached statistical significance, perhaps due to attrition. The researchers acknowledge that the cognitive improvement they found could have resulted from subjects’ increased experience with the tests.

Artifact, not drug impact
This need to disentangle practice from medication effects initially inspired the Goldberg study. According to Goldberg and colleagues, “large industry-sponsored controlled trials” in patients with first-episode schizophrenia found that risperidone and olanzapine significantly enhanced cognition, with effect sizes on composite measures ranging from 0.35 to 0.54. “Critically, these studies did not include control groups, raising the possibility that improvements were due to practice effects because patients were tested on multiple occasions,” they write.

In addition, many of the subjects had a history of taking medication. Their test performance may have improved because, at baseline, they were undergoing withdrawal from prior treatment or were taking medication that hampered cognition.

The Goldberg team sought to address these problems by recruiting 104 subjects with first-episode schizophrenia (FES) and randomly assigning them to 16 weeks of treatment with olanzapine or risperidone. They also enrolled a healthy control (HC) group of 84 subjects who received no study medication.

All subjects underwent cognitive testing at baseline, 6 weeks, and 16 weeks. Researchers who were blind to group assignments tested their mental status, processing speed, motor speed and dexterity, episodic memory, working memory, and executive function.

The risperidone and olanzapine groups improved equally over time, so analyses combined them. Cognitive performance improved on nine of the 16 measures. Strikingly, the medicated and control groups made similar gains on most of them. In fact, treated subjects’ rate of improvement surpassed that of controls only on the trail making and memory for visual designs tests.

Across the 16 measures, composite effect sizes—0.33 for unmedicated healthy subjects and 0.36 for medicated subjects with schizophrenia—unearthed little improvement beyond that attributed to practice. “It is sobering to note that the composite effect size in the FES group of 0.36 would be considered moderate and could be attributed to treatment,” Goldberg and colleagues write. Even so, they deem their results “circumstantial” because ethical concerns precluded testing untreated subjects with schizophrenia.

What about social cognition?
Most studies of whether antipsychotics help cognition in schizophrenia have focused on basic cognitive processes such as memory and attention rather than social cognition, the ability to perceive and process information about oneself and others. Since the limited research has yielded unclear results, a study in this month’s American Journal of Psychiatry, led by Mark J. Sergi of California State University at Northridge, assessed the effects of three antipsychotic drugs on both social and basic cognition.

The double-blind study assigned 100 subjects with schizophrenia or schizoaffective disorder to 8 weeks of treatment with risperidone, olanzapine, or haloperidol in a modified random design. They underwent testing at baseline, week 4, and week 8.

The social cognition measures probed the ability to perceive interpersonal and emotional cues, like those conveyed by tone of voice, facial expressions, and gestures. Analyses treated them as a single cluster defined a priori.

Neither social cognition nor the processing speed factor showed significant effects of treatment, time, or their interaction. “However, general cognitive ability improved over time for each medication, an effect that may be attributable to the increased test familiarity and practice effects from repeated testing in an 8-week period,” Sergi and colleagues write.

The ramifications
The four new studies agree that none of the tested antipsychotics outshines the others in relieving cognitive deficits in schizophrenia. Actually, the Goldberg and Sergi studies suggest they do little for overall cognitive functioning. These drugs—or at least risperidone and olanzapine—may help only trail making and episodic memory for visual designs. These findings could lead to a rethinking of molecular targets for interventions.

“We hope that our findings increase awareness of practice effects as a potential source of cognitive change in clinical trials,” Goldberg and colleagues write. They call for the development of research methods and tests that minimize practice-related bias. They contend that the drug discovery and approval process could benefit from the inclusion of a healthy control group in trials assessing cognitive change. Beyond future research, the Goldberg team writes, “Our study may have implications for the reinterpretation of several previous trials in which cognition improved because the magnitudes of improvement found in prior trials may not be greater than the practice effect demonstrated by the HC group in our study.“—Victoria L. Wilcox.

As stated in the CATIE and CAFÉ neurocognition manuscripts, it is possible that the small improvements in neurocognitive performance following randomization to one of the antipsychotic treatments in these studies are due solely to practice effects or expectation biases. This statement is affirmed by the excellent recent study by Goldberg et al. in which improvements in cognitive performance were almost identical in magnitude to the practice effects found in healthy controls. While these data may be perhaps disappointing to the hope that second-generation medications improve cognition, they may also suggest that cognitive performance is less recalcitrant to change than previously expected.

In the context of a double-blind study design, the degree of cognitive enhancement observed for each treatment group is a function of three major variables: treatment effect, placebo effect, and practice effect. In studies of antipsychotic medications without a placebo control group, practice and placebo effects in schizophrenia cannot be disentangled from treatment effects. They also cannot be disentangled from each other. Recent data from a double-blind study comparing the effects of donepezil hydrochloride and placebo in a highly refined sample of 226 patients with schizophrenia stabilized while taking second-generation antipsychotics suggested that patients taking placebo had neurocognitive effect size improvements (0.22 SD after being tested twice over 6 weeks; 0.45 SD after the third assessment at 12 weeks) on the same test battery used in the CATIE and CAFÉ studies, suggesting a practice or placebo effect (Keefe et al., Neuropsychopharmacology, in press) consistent with the improvements reported in the CATIE and CAFÉ treatment studies. These cognitive improvements are in contrast to test-retest data collected in patients with schizophrenia tested with the MATRICS Consensus Cognitive Battery (MCCB; Nuechterlein et al., in press) and the Brief Assessment of Cognition in Schizophrenia (BACS; Keefe et al., 2004), which showed very little practice effects. The contrast of the data from these test-retest studies that did not involve the initiation of new treatments with cognitive improvements following the initiation of antipsychotic treatment or placebo suggests that attribution biases beyond simple practice effects may be at work.

Test-retest data from patients tested twice within a briefer period than the test interval in the four treatment studies discussed above suggest that schizophrenia patients demonstrate relatively small improvements in executive functions (Keefe et al., 2004; Nuechterlein et al., in press) and the WAIS digit-symbol test (Nuechterlein et al., in press), and medium improvements on tests of verbal memory only when identical versions are repeated (Hawkins and Wexler, 1999; Keefe et al., 2004) but not on tests of verbal fluency (Keefe et al., 2004; Nuechterlein et al., in press). In the donepezil/placebo study, patients who received placebo improved substantially across several cognitive domains. Although not tested directly, this series of results suggests that the magnitude of placebo effects in cognitive enhancement trials may exceed the reported size of practice-related improvements in studies of schizophrenia patients tested twice without the prospect of the initiation of a cognitive intervention.

The greater improvements in cognition found in the context of a placebo-controlled trial could be due to a variety of psychological factors. When a patient enters into a trial or is treated with a medication that is believed to contribute beneficially to cognitive performance, rater bias and expectation bias can have strong effects on performance. Patients who are told that their cognitive abilities might improve may be able to perform better on the test batteries used in the study simply because their expectations become more optimistic. Second, testers who believe that a patient will have cognitive improvement, or hope for such improvement, could administer the tests in a more hopeful, positive manner, which can help the patient raise his or her expectations for performance and thus engage motivational systems that were previously disengaged (Keefe, 2006). Such expectation bias can also lead to inaccuracies in scoring; since many cognitive tests require the use of judgment to determine final scores, hopeful testers are more likely to give the “benefit of the doubt” to patients after they have entered into a study in which the treatment is potentially cognitively enhancing. Third, this same type of expectation could have an impact on the support that a patient receives in his or her community/living situation. If the people who interact regularly with the patient begin looking for better performance on cognitively related tasks, these expectations could become self-fulfilling in that they may raise the confidence and motivation of the patient to perform well on such tasks, including cognitive testing.

The factors associated with improvement during a placebo-controlled trial are indeed complex, and it is difficult to distinguish practice effects from placebo effects. However, the relatively small clinical improvement in test-retest designs without treatment or placebo intervention suggests that any potential practice effects may at least be potentiated by placebo effects.

The implications for this series of results include a methodological caution and a reason for optimism. Regarding the caution, future trials of cognitive-enhancing compounds might need to be designed in such a way that practice and placebo are reduced. Very few treatment studies of patients with schizophrenia have employed a priori methodological strategies to reduce the magnitude of potential practice effects, such as the use of a placebo run-in period with one or more administrations of the cognitive battery prior to randomization. Regarding the optimism, these studies suggest that schizophrenia cognition (perhaps especially when freed from the dampening effects of large doses of high potency medications such as haloperidol) could be more plastic that had been previously assumed; it is possibly as sensitive to experience-dependent learning in schizophrenia patients as healthy controls, and it may benefit from improved psychological expectations. While this is a methodological nuisance for clinical trial designs, it may also reveal an unexpectedly large potential gain for psychological interventions such as cognitive remediation, cognitive-behavioral therapy, and even encouragement.

This article questions the prevailing notion that antipsychotic medication (particularly second-generation antipsychotics) improve cognitive functioning in individuals with schizophrenia. As the authors rightly note, practice effects should be taken into account before attributing improvements to drug effects.

I propose that future studies should use computational cognitive assessment tools like CANTAB or CogTest, which have at least two advantages. These tools have multiple similar test modules, so on each testing during one study, participants get a similar but not the same test to assess the same cognitive function. Besides, computational assessment also reduces chances of subjective bias on the part of investigator.

One remedy would be repeated practice over time before the actual baseline, sufficient to reach asymptotic ability. Computerized testing of reaction time measures, short-term memory span, etc. would all be quite cheap and easy to implement, for example, as a weekly session.

We recently completed a meta-analysis on "Longitudinal studies of cognition in schizophrenia" (to be published in the British Journal of Psychiatry) based on 53 studies providing data for 31 cognitive variables. When enough data were available (19 variables from eight cognitive tests), we compared the results of schizophrenic participants to those of normal controls.

Given the differences in methods and the fact that most of the studies included in our meta-analysis reported results of patients being past their first episode (FE), it is surprising how close our results and conclusions are compared to those of Goldberg et al. In our analysis we found that, with two exceptions (semantic verbal fluency and Boston naming test, which were stable), participants with schizophrenia improved their performances. The improvement was statistically significant for 19 variables (out of 29).
However, controls also showed improvement in most of the variables due to the practice effect. A significant improvement (definite practice effect) was present for 10 variables, an improvement that did not reach significance (possible practice effect) was present in six more variables, and three variables showed no improvement. When compared with schizophrenic patients, controls showed similar improvement for 11 variables, significantly more improvement for seven variables (six of them from the “definite practice effect” group, one from the “possible practice effect”) and for one variable less improvement (the Stroop interference score). Thus, these results suggest that for most of the cognitive variables, improvement seen in schizophrenic subjects does not exceed improvement due to the practice effect.

It is interesting to mention that in our analysis only two variables improved significantly more when patients had a change in their medication from first-generation antipsychotics (FGAs) to second-generation antipsychotics (SGAs). These variables were time to complete TMT B and the delayed recall of the Visual Reproduction (from the WMS). In the Goldberg et al. study the only two tests that showed more improvement in schizophrenic subjects than in controls were also the TMT and visual reproduction. Although in our study schizophrenic subjects did not improve more than controls, the two results (Goldberg’s and ours) taken together could be an indirect argument for a differential, specific effect of SGAs on those two (visuo-spatial) tasks. The placebo effect—see the comment by Richard Keefe—could explain why improvement in the study by Goldberg et al. was greater than in our meta-analysis. Studies of effects of changing medication in the opposite direction, from SGAs to FGAs, could contribute to validate or invalidate these hypotheses.

Goldberg et al. suggested that there could be a set of task characteristics that could be used to develop tasks resistant to the practice effect. Our own results are less optimistic as they show that phonemic verbal fluency, despite a very similar format, does not share the “practice resistance” with the semantic verbal fluency. However, we think that there is already a wealth of data that could be used to select the best cognitive tests. An alternative solution is the use of scales and questionnaires for evaluating cognition (that are sensible to the placebo effect but not to the practice effect).

The Lieberman et al. CATIE study is a landmark large-scale clinical trial of antipsychotic drug therapy and will generate considerable discussion in the coming months. It offers important insights about real-world treatment of individuals with the diagnosis of schizophrenia, in the sense of typical practices in clinics around the country and the clinical experience of many practitioners. It probably comes as no surprise that the response to available antipsychotic agents is suboptimal and that differences between drugs are not dramatic in many cases.

One of the questions that comes to my mind about the results is whether and to what degree they are generalizable. Do the results of this study accurately characterize the effects of these drugs across the spectrum of patients with chronic schizophrenia who are treated with them? In other words, are the patients in the CATIE trial representative of the patients with chronic schizophrenia who are in need of these medications? I believe there are several indicators to suggest that they may not be. First, of the subjects in this trial, most of whom (75 percent) were male, 40 percent had been or were married. Second, the mean age at first antipsychotic treatment was 26 years. Third, 30 percent of the subjects were on no medication when they entered the trial. These are all somewhat atypical characteristics in my experience, especially for a predominantly male sample.

In the NIMH schizophrenia genetic study that I direct, we have extensively evaluated over 600 subjects with schizophrenia from around the country. In our sample, the mean age at first antipsychotic treatment is 21 and the ever-married rate is 15 percent, and our sample is one-third female. Moreover, less than 10 percent of our sample is unmedicated at the time that they are evaluated. The finding that a mean dose of 20 mg of perphenazine was as effective as other medications also is somewhat surprising in my experience, as having used this drug for many years, I have rarely seen chronic, actively symptomatic patients respond well without dosing around 32 milligrams and above. Is it possible that the CATIE trial inadvertently enrolled patients more in the schizophrenia spectrum end of the distribution of patients receiving these drugs who may tend not to show as clear benefit? Or maybe the size and breadth of the CATIE trial obscured the signal from the more classic patient with schizophrenia for whom antipsychotic treatment is essential.

It will be interesting to see whether other academic schizophrenia centers concur with the demographics of my experience as noted above or those of CATIE. Multicenter studies—and CATIE involved 57 centers each contributing relatively small samples over a 2-year period—are susceptible to dilution effects and to the possibility that the sample is clinically "noisy." It will be interesting to see, when data analyses from the next stages appear, whether differences are found in the results from different centers who participated in the trial. Will CATIE have told the story of how these drugs work in patients who receive them, or will it have failed to identify the signal from the noise?

I also have not seen the response at that dose of perphenazine and even the atypical antipsychotics in chronic schizophrenics. In fact, the only medication that seemed to have an adequate "real-life" dose was olanzapine.

It seems that the doses used are not equivalent,
and the researchers have used somewhat lower doses of perphenazine and risperidone (in favor of olanzapine). Thus, it is obvious that perphenazine and risperidone have showed smaller efficacy.

There is evidence that the Chinese traditional medicines may be an alternative approach in the treatment of schizophrenia. Our recent studies indicate that the extraction of gingko biloba may increase the effectiveness of antipsychotic drugs, but reduce their side effects. This finding may provide a new clue to develop a novel therapeutic drug for treatment of schizophrenia.

Reply to Dr. Weinberger's questions about the generalizability of the CATIE sample, by
Marvin Swartz, for the CATIE investigators
As CATIE investigators, we have been mindful of concerns about the generalizability of the CATIE sample. In response to a similar concern, our colleague Jeffrey Swanson at Duke compared CATIE participants to a quasi-random sample of 1,413 patients enrolled in the Schizophrenia Care and Assessment Program (SCAP), an observational, non-interventional study of schizophrenia treatment in usual care settings in the United States. The two samples were similar in demographic characteristics, e.g., gender (70 percent male in SCAP, 74 percent male in CATIE), age (mean age = 43 years in SCAP, mean age = 41 years in CATIE), and education (36 percent of SCAP participants had a high school education and 28 percent attended college; in CATIE these percentages were 35 percent and 39 percent, respectively). The CATIE study had a lower proportion of participants from racial minority backgrounds (40 percent vs. 54 percent).
The samples also resembled each other in clinical characteristics. Nearly one-third of the patients in both studies had recently been hospitalized. The CATIE sample had slightly higher average scores on psychotic symptom severity than the SCAP patients (mean PANSS total score = 75 vs. 71), and also slightly higher scores on functioning and quality of life (mean Heinrichs-Carpenter QLS score = 63 vs. 57) (Haya Ascher-Svanum, Ph.D., Senior Research Scientist, Eli Lilly and Company; personal communication). These similarities provide some confidence that CATIE’s RCT design did not result in a biased selection of patients.

The antipsychotic drugs mainly treat psychosis (in contrast to cognition impairments and primary negative symptoms). In the CATIE study, the drugs tested share the same mechanism of action (D2 antagonism). Clozapine aside, the second-generation drugs (SGA) have not established superior efficacy over first-generation drugs (FGA). The FDA has granted no such claim, and the Cochrane reviews do not support superior antipsychotic efficacy. The appearance of superiority, including the terrific organization of data in the Davis meta-analyses, may be extensively based on last observation carried forward, excessive dose of the FGA, failure to pretreat with anti-parkinsonian drugs, sponsor bias, and a number of other methodological problems including the fact that most study subjects are doing poorly on FGA when recruited into comparative studies. "Atypical antipsychotic" means only low extrapyramidal symptoms at therapeutic dosing. In this regard, the CATIE findings are not surprising, but simply point to the considerable shortfall in effectiveness associated with current treatments. The drugs will vary considerably along side effect liabilities, and matching patient to side effect profile is the key to individualizing drug choice at the moment.

As to time on drug, there was not a long-acting depot arm to the study, and this method should probably be considered in substantially more patients than is the practice in the U.S. Olanzapine did a little better on the time on drug measure, and risperidone was second. This may relate to the fact that these were the two most common drugs used at study onset, so more patients with known tolerability to these drugs began the trial. In any case, concern with weight and the metabolic syndrome will drastically cut the time on drug for olanzapine in current practice.

It is almost impossible to have a level playing field in comparative drug studies, since optimal dosing and individualized dosing parameters are simply little known with most antipsychotic drugs. In this regard, we don't know if quetiapine and ziprasidone would have done better at higher dose; or if risperidone being yoked to olanzapine led to suboptimal dosing in many cases. In Rosenheck's JAMA report, he observed that pretreatment with an anti-parkinsonian drug led to similar effectiveness comparing olanzapine with haloperidol. Would perphenazine have been even better with anti-cholinergic pretreatment?

In my view, this is a critically important study in that it reasonably represents an effectiveness study in typical settings [probably more representative than the Weinberger data set (see Weinberger commentary)] without sponsor bias. As such, it has succeeded in calling public attention to the relative lack of progress associated with "me-too" dopamine blocking antipsychotic drugs. This conclusion is reinforced by the U.K. study reported by Peter Jones at the ICOSR where SGA did not beat FGA on the primary endpoint (quality of life) or on many secondary measures. Another head-on comparison study with public support.

My hope is that industry will devote discovery resources to the challenging problems of novel treatments with new molecular targets addressing problems with impaired cognition and primary negative psychopathology. Refining antipsychotic drugs has not advanced therapeutics much since the introduction of chlorpromazine. Reducing the neuroleptic adverse effects of FGA is a real advance, especially considering the excessive dosing. But significant new liabilities are associated with some of the SGA. We now need to meet the efficacy challenge for the components of schizophrenia that mainly cause poor functional outcomes.

Dr. Swarz's comment providing data from the SCAP study is helpful in confirming that CATIE patients are similar in many phenomenological respects to other patients in schizophrenia treatment programs. Indeed, in terms of PANSS ratings, sex ratios, age at enrollment in the study, and history of recent hospitalizations, CATIE patients are not substantially different from patients we see at the NIH in Bethesda, Maryland and we saw when our program was located at St. Elizabeths Hospital in Washington, D.C. In my comment, I asked specifically about three CATIE characteristics that seemed atypical to me: age at first antipsychotic treatment (26), precentage of patients who were or had been married (40%), and percentage of patients who were unmedicated at the time they volunteered for the study (30%). It would enlighten this discussion if Dr. Swarz would report these data from the SCAP study.

It would be interesting to learn from Dr. Swartz and the CATIE investigators (a) the age at first antipsychotic treatment, (b) the percentage of patients who were or had been married, and (c) the percentage of patients who were unmedicated at the time they volunteered for the study in the SCAP sample. I suspect these three variables, if available, will more closely resemble those of the CATIE trial sample than the CBDB sibling study sample.

Dr. Weinberger has suggested that the CATIE trial inadvertently enrolled patients more in the schizophrenia spectrum end of the distribution, or maybe the size and breadth of the CATIE trial obscured the signal from the more classic patient with schizophrenia, so the results may not be generalizable. I suspect that differences in criteria for recruitment and retention between the CBDB sibling study and the CATIE study explain the differences among the demographic variables of the samples.

The clinical characteristics of the CBDB sibling study sample are what one would expect in a study whose purpose is to find associations between genetic variation and neuroimaging/neuropsychological phenotypes, among affected and unaffected family members. The usual patient included in the CBDB sample probably: had onset of active symptoms in late adolescence or early adulthood (i.e., high school or college age, before many people marry); was started on medications earlier in life; and had more intact nuclear families (parents, siblings, etc.) than the usual CATIE subject. Patients with later onset of illness or milder symptoms (who are more likely to be or have been married) and who did not start on medications once psychotic symptoms occurred, were less compliant with their medications, and/or had fewer intact family relationships were unlikely to successfully travel to Bethesda and complete two full days of research testing. The CATIE recruitment strategy did not exclude the unusual patient with treatment of symptoms later in adulthood, require intact nuclear family, or require compliance with medications at time of study entry.

The CBDB sample better represents a "textbook case" of schizophrenia. Many patients who do meet DSM-IV criteria for schizophrenia may not be good candidates for a genetics study, but may still have schizophrenia and are appropriate candidates for a large clinical study. This would suggest that the findings can be generalized to other groups of patients with the illness, though perhaps not the "classic" cases of schizophrenia gathered in the CBDB study.

Reply to comment by Johann Samuhanand
To our best knowledge, there is no published evidence that gingko biloba could be useful in reducing the side effects of clozapine and other atypicals. However, using the same group of patients with schizophrenia as we reported previously (Zhang et al., 2001), our recent study has shown that chronic patients with schizophrenia demonstrated significantly lower CD3+, CD4+, and IL-2 secreting cells, together with CD4/CD8 ratio, than did healthy controls at baseline. After a 12-week treatment, EGb added to haloperidol treatment increased the initially low peripheral CD3+, CD4+, and IL-2 secreting cells, together with CD4/CD8 ratio. There was only a significant increase in CD4+ cells in the placebo plus haloperidol group. These findings suggest that ginkgo biloba may improve the decreased peripheral immune functions in schizophrenia (Zhang et al., 2006).

As we have known, although clozapine is superior over the other drugs in terms of efficacy, it can severely deplete white blood cells, leading to limitations on its use. If gingko biloba may indeed produce beneficial effects on the immune system in schizophrenia, there is a possibility that ginkgo biloba may be useful in reducing the side effects of clozapine, at least in regard to immune function.

On the other hand, a limitation of the design of our previous study (Zhang et al., 2001) is the use of haloperidol as the antipsychotic treatment at a time when atypical antipsychotic drugs are the standard of care. Therefore, a further study is warranted to investigate whether ginkgo biloba shows similar benefits in augmenting the atypical antipsychotics, which already have the capacity to improve the positive and negative symptoms and have better profiles in terms of extrapyramidal side effects.

I recommend this clear and well-written paper for students to understand the basis of the CATIE studies.

I agree with Dr. Weinberger about the variables that could obscure the results in the target population or the schizophrenic population. His remarks about the control conditions or the dissection of the variables in the study are important. The difference between typical and atypical drugs is clear in these data.

New drugs, diferent from the typical and atypical drugs, based on new genetics research and new genetic routes must be developed in order to achieve new successes in the treatment of schizophrenia.

I think that atypical antipsychotics do not mean only low extrapyramidal symptoms at therapeutic doses.
Several studies have demonstrated that atypical drugs(especially olanzapine) are better than typical drugs in important characteristics such as cognitive functioning.

The most important current development of new antipsychotic drugs is focused on two mechanisms, the α7-nicotinic receptor agonists that are good new candidates for the management of the disease (Martin et al., 2004) and, most recently (and I think probably the closest to development), is the one that focuses on glutamatergic neurotransmission (Coyle and Tsai, 2004).

On the other hand, I think that behavioral and cognitive therapy, as well as family support and family management given by a professional in this area of health, are important to ensure an excellent result in schizophrenic patients.

Comment by: Robert FisherSubmitted 24 December 2005
Posted 28 December 2005 I recommend the Primary Papers

[Disclosure: R. Fisher was Study Coordinator, Recruiter, and Diagnostician for the Byerly Group at UT Southwestern CATIE site, the second-largest enrollment site in the study.]

The CATIE study is likely the best designed and implemented research project ever conducted regarding schizophrenia and relevant psychopharmacology. The extensively collected data will have an enormous heuristic value in the study and evaluation of this disorder in all aspects of schizophreinia. I found Drs. Lieberman and McEvoy to be true professionals in this study design.

Implicit in the findings of Schmid et al. is the idea that the relationship among ligand, receptor signaling, and cellular context is an extremely complex one that will take a great deal more work to tease out. Thus, Dr. Bryan Roth has proposed on a number of occasions (see, for example, Gray and Roth, 2007; Abbas and Roth, 2005) that novel approaches for drug discovery may prove more effective in producing schizophrenia drugs that have greater therapeutic efficacy with lower side effect liability. Since it will likely be many years before the field has a detailed understanding of the "nitty-gritty" of the receptor signaling and trafficking relevant to schizophrenia and its treatment, we have suggested a number of approaches that are less reliant on such information.

For example, approaches based on screening for drugs that either mimic the gene expression profiles of gold standard drugs such as clozapine or normalize schizophrenia-associated changes in gene expression are being explored. Another approach is behavior-based screening, in which targeted screens are performed with drugs to find those that have efficacy in animal disease models. A further related approach, exemplified by Psychogenics' Smartcube(TM) (the associated database is called Smartbase[TM]) involves injecting drugs and monitoring the resulting behavior using computer-based machine learning to generate a multidimensional behavioral signature for gold standard drugs. Drugs can then be screened to look for those that mimic gold standard drugs in terms of their signatures. Though Psychogenics does not appear to have done much (at least publicly) with this approach, it represents the sort of innovative thinking that may prove fruitful in future behavior-based drug discovery efforts since it is not dependent on knowing anything about the mechanism. In the end, at least in the near future, we believe such approaches may prove extremely useful in drug discovery efforts since they do not rely on extensive mechanistic knowledge of the processes underlying schizophrenia.

The authors suggest that they have found what could be considered the Holy Grail of cognitive research—a means to enhance intelligence. There is some hope from the article, as results on a task considered to measure fluid intelligence are improved, even if the subjects are not trained on this specific task. The “dual n-back” training task, although not pure working memory (as the authors acknowledge), is a very interesting experimental paradigm. Unfortunately, the authors fail to convince us of its usefulness in enhancing “fluid intelligence.” When a drug is tested, any effect, to be convincingly supported, must be demonstrated in a double-blind, randomized, placebo (or standard treatment)-controlled trial. The same should be true for any (pharmacological or otherwise) means aimed at enhancing cognition.

As for the issue of whether this training will have the same effects in schizophrenic subjects as it had in these normal, motivated controls, that is an entirely different question that is not addressed in the article. I think that future studies have to address all those limitations (randomization of subjects, a similar amount of training with a different task in controls, a double-blind design) before any firm conclusions could be drawn.

This paper is further evidence of an important and laudable new trend in schizophrenia psychopharmacology: namely the development and test of compounds on the basis of their relationship to circuit abnormalities, evidence derived from postmortem, genetic, and animal model studies. The authors based their choice of MK-0777 for test in schizophrenia on evidence for decreased cortical GABA neurotransmission onto pyramidal neurons at receptors having the α2 subunit, and other evidence pointing to the GABA-pyramidal neuron interaction as important in cognition and in generation of γ band oscillations. In this add-on, double-blind placebo study, the Ns were underpowered and more subjects need to be studied to be certain about clinical effects. However, one test, the Preparing to Overcome Prepotency Test (POP), had significant improvements in response latency and showed concomitant improvement in increased frontal γ band activity induced during the task, although not meeting the criterion for statistical significance. POP requires subjects either to “go with the flow” (indicated by a green light) and respond in the same direction as an arrow, or when cued by a red light to “go upstream” and point in the opposite direction, a test previously used in the Cho et al. 2006 PNAS paper and found to be accompanied by increased induced γ band oscillations.

γ band activity has justifiably attracted considerable attention, since there is mounting evidence of its relevance to human cognition as well as to basic neuroscience studies of neuronal assembly communication. Its important basis in the GABA cortical neuronal interaction with pyramidal cells makes it especially fascinating in schizophrenia. However, an important caution light was recently flashed by Yuval-Greenberg et al. in an article in Neuron (2008) in which they presented strong evidence that apparent increases or decreases in the “induced γ band oscillations” (those not temporally linked to a response or stimulus) could be the result of the eye muscle activation associated with small saccadic eye movements, “a saccadic spike potential” that could be confused with γ band oscillations. The Yuval-Greenberg article appeared too late for the authors to discuss in the present paper, but its implications for future work using induced γ are important. For studies of induced γ, we all will have to begin using eye movement measures sensitive to mini-saccades. Those of us who measure γ phase-locked to measureable events, such as sensory stimuli or responses, appear to be off the hook since we condition on known events, unlike conditions where induced γ is measured.